1. Field of the Invention
This invention relates to the measurement of liquid flow by the counting of incremental flow volumes. More particularly, it relates to a method of measuring the liquid consumption of laboratory animals which involves a counting of licks from a drinking tube and apparatus useful in the practice of the method.
2. Description of the Prior Art
In the utilization of laboratory animals for various experiments, one of the parameters which frequently must be monitored is the animal's liquid consumption. Obviously this could be done by labor-intensive means such as having the animal drink from a calibrated source, the level of which is read from time to time. However, such a method--while giving total consumption over the period between readings--will give no continuous consumption profile nor meaningful rate information. Furthermore, such a method does not permit linkage to a computer such as by creation of a signal which can be converted into standard digital logic pulses.
Current methodology utilizes a drinking monitor which relies on having the animal complete a circuit when it takes liquid from a source such as a standard drinking tube. The tube is connected to a source of low current electric potential, as is the floor of the drinking station upon which the animal will stand when drinking. Touching of the source by the animal completes the circuit. The monitor, in effect, counts and records the frequency of circuit closure and sometimes length of closure as well. These, when correlated to the drinking habits of particular species of animals, measure volume consumed.
Such systems are indeed linkable to computers and are not labor-intensive. However, from their very nature, an electrical current (albeit of an order of magnitude of 4 microamperes or less) must pass through the body of the animal.
These prior art devices, while relatively sophisticated, have their own peculiar problems. The electrical currents can affect the chemistry of the liquid being fed to the animal as well as its perceived taste. Furthermore, the liquid and the drinking tube both have to be conductive to insure operability. Additionally, the existence of a fluid meniscus can cause constant contact reports thus effectively immobilizing the system. But the most important disadvantages of such systems hinge on the necessity for having current flow through the body of the animal. There is no real certainty about the long range effect on animal behaviour of such frequent flow of current through its body. Also, it is impossible to conduct meaningful experiments involving bioelectric stimulation, foot shock or attached cutaneous electrode shock simultaneously with animal drinking without thereby creating interference.
Consequently, a need exists for some method of monitoring the liquid consumption of a laboratory animal which is accurate, which counts every lick of liquid from a drinking tube and which, while computer linkable, does not depend either on passing current through the body of the animal or on the conductivity of the system components and of the liquid itself.
While no patent search has been made, it is believed that the prior art is fairly summarized above.